1. Field of the Invention
The present invention relates to a technology for improving a response speed of image reading device and an image forming apparatus when returning from an energy-saving mode.
2. Description of the Related Art
An image forming apparatus such as a printing machine, a copier, a printer, and a facsimile that is typically used has recently become widespread at offices or at home for the reasons of reproducibility, stability of images, and the like. It is general that this type of image forming apparatus operates with its utility system of keeping power on as the nature of the product. More attention is paid to improvement of its availability than reduction of energy consumption. Now, a problem of energy consumption has become evident, however, there is a need of a reduced consumption of energy or inhibited use of exhausted energy source such as fossil fuel that affects global warming.
Japanese Patent Application Laid-open No. 2004-343394 proposes an image forming apparatus, which, in image forming apparatus in which an operating display unit is controlled by different central processing units (CPU) based on extension modes of an application of processing image forming, increases response speed when returning from an energy saving mode, in which a power supply is limited to a necessity minimum, by controlling the operating display unit by a CPU having a shorter initial operating time among plural CPUs controlling the operating display unit, when supplying power to the operating display unit to start the image forming apparatus, and a method of driving the operating display unit.
Japanese patent Application Laid-open No. 2004-246298 proposes an image reading device and an image forming apparatus, which, in image reading device and image forming apparatus having a carriage movable in the scanning direction of a document that is mounted with a light source irradiating a document and a mirror directing a reflected light from the document irradiated by the light source, a sensor detecting a home position of the carriage, and a line sensor reading images of the document based on the reflected light from the mirror, when aligning the carriage through homing processing, check whether it is a press scan mode and provide a quick start, if in the affirmative, instead of homing operation when the sensor detects the carriage.
Japanese Patent Application Laid-open No. 2004-112718 proposes an image processing apparatus, which, in image processing apparatus that can shift to the energy-saving mode, includes a CPU performing integral control of the whole apparatus, an energy-saving control unit having a function of returning from the energy-saving mode to a normal operation mode and smaller power consumption than the CPU, and a detecting unit of detecting a return trigger from the energy-saving mode. When shifting to the energy-saving mode, the image processing apparatus can reduce power consumption in the energy-saving mode by supplying power only to the energy-saving control unit and the detecting unit and return from the energy-saving mode to the normal operation mode in a shorter time.
Japanese Patent Application Laid-open No 2003-219127 proposes an image reading device, which, in image reading device photoelectrically converting images of a document at a reading unit including an optical system mounted on a charge-coupled device (CCD) and a moving mechanism and enabling an image reading condition, such as black level and white level of photoelectrically converted image signals to be set, includes an unit of setting an image reading condition and an unit of storing the set image reading condition when shifting to the energy-saving mode, and when returning from the energy-saving mode, can set the stored image reading condition and read images, as a result, to have a shorter time to return from the energy-saving mode instead of adjusting the image reading condition.
Japanese Patent Application Laid-open No. 2001-265161 proposes a fixing device, which controls changing the number of supplied sheets in starting copies-per-minute (CPM) down control based on a fixed temperature when starting supplying sheets immediately after reloading to improve fixing quality without any control difference immediately after reloading.
However, the conventional technology has the following problem. When a traveling body that scans a document is moved to a home position, the conventional image forming apparatus shifts to the energy-saving mode. When returning from the energy-saving mode, therefore, it is necessary to move the traveling body for performing auto-gain-control (AGC) processing to a position at which a white reference board is installed and it takes more time to return from the energy-saving mode due to the moving time.